Improvement in beam-compasses



` Patented Feb. 2l, 1871.

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Dividers.

IW en La r n 1 SW m positions.

ofthe scales.

TOS-TAH LYll/IAN, 0F LEANOX. MASSACHUSETTS.

Letters Patent No. 111,954, dated February 21, 1871.

IMPROVEMENT IN BEAM-COMPASSES.

The Schedule Vreferred to i:x.these Letters Patent and making part of the'same.

To all whom it may concern: 'i

the-county of Berkshire, in the State of Massachusetts, have invented a new and Improved Draughting Instrument, which call Scale-Dividers; andv I do hereby declare that the following is a iulland exact description thereoi, reference being had tothe accompan ying drawing and to the letters 'of reference marked thereon.

My invention consists in making the-.beam of the .dividers a finely divided scale, `with the ypen o1' 'pointholder permanently pivotcd to one end, so 'as to con-.

stituteone leg'nicely adjustable, whose motion isat the sametime, capable of the-mostaccnrate measurement, while the other leg, embracing a sliding index, a friction-clamp, and spring, with thumb .and foot pieces, is susceptible oi' any desired degree of smoothness and delicacy of motion. l Thus each 'of the parts is rendered far more convenient, reliable, effective, and or" either can be vby .itself alone.

To enable others skilled in' the art to comprehend and use my-invention, I will describe in detail its construction and application.

Figure l represents a longitudinal section of theinstrument, with the first form of the micrometer attachment, and the sliding leg inits several parts and Figure 2 shows a side elevation of the same, with the graduation of the visible side of `the beam, with openings and index marks in thc sliding leg for each Figure 3 gives a longitudinal section of the iirst form ofthe micrometer-piece M, with its elongated orifice, E, for the v M S. l

Figure 4 gives aside elevation end viewof the instrument. l v

Figure 5 gives 'a longitudinalV section of both pen and point-holder, as far down as the under border of the beam, to which point the two are identical, including themanuer ot'its attachmentjto the beambv means of the steel pivot l?.

i, Figure 6 represents a longitudinal section of the in-` strument with the second form of the micrometer attachment, showing the form of the micrometer-piece M, with its nut N', gear-screw G, micrometer-screw M S', and spring S'. y

Figure 7 shows a side elevation or" the same.

Figure 8, a, is an end 'view of the same, with the gear, and micrometer-screws, andv nut, all in their normal positions'. l

Figure S, 1),.is thc same, with these parts removed.

Figure 9 is a hirds-eyc view of' the same.

Figure-.10 gives side elevations oi' the pen P n; a, showing. the-micrometer'side; i), the yopposite side; and c, a. longitudinal section of the same.

Figure 11 presents a transverse section of the slidoi' the same iu the greater variation than action and play of -the micrometer-screw ,y ing index, with its four oriliees o o o, for reading the A Be itknown that l, J osrarr LYMAN, of Lenox, in"

several scales.

Figure 12 exhibitsa side elevation of the extensionclam p for joining two beams, so as to give the instrument any desired length. p L

Figure 13 gives a transverse section ofthe same. lhebeanr B, iigs. 1 2 6 7 9, -consists of asteel plate of any desired length, from two to twelve inches, threetenths of anjnch wide, and one-sixteenth of an inch thick, 'graduated accuratelywith four scales, viz.

two on each side.

Near .one end of this, by means of `the steel pivot P,

is attached the peu Pu, or point-holder P h, tige-l 2 5 o 7 97.10.

(llose by its upper end', iu theirst form, figs. 15,` is a' veryfine-tlneaded `scre\v,made of bronze, forthe adjustment of the'micrometer-screw M S.

The axis of this screw and the pointl of :the pen or -holder are nearly equidistant from the center of the pivot P. Hence the threads ofthe former are made either 4to correspond in distance with thelength of the divisions of the several scales, lor to have akuown and convenient ratio therewith. For instance, if the threads of the 'micrometer-screw are one-fortieth of an inch, the point of the pen or helder Iwould vary one-fortietlr-oi' an inch, equivalent tove two-hundredths of an iuch,'at4 each revolution. Therefore, one-fifth of a revolution would give onetwo-hundredths ,of aninch; i. c., if hall' aninoh is taken as the nuit, one'one-hundredth thereo Or, ifthe fourth of an inch-is taken as the unit, one-tenth of -a revoluf v nonwonld give one one-hundredth of the unit.

`These divisions are shown in the milled-headed micrometer-screwM' S, iig. 4.

Bntif the threads ofthe micrometer-screw are onesixtieth of an inch, and the distance of itsaxis below the axis of the pivot isone-iifth of an inch, while the point of the peu or holder is six times this distance, as shown in the. secondform of the attachment, figs. 6 7 8, one revolution of the micrometer-screw would vary the point of the pen or holder one-tenth of an inch, orone-tenthoi' a revolution wou-ld vary the same one one-hundredth of an inch; .and one-fortieth of a revolution would vary it one-fourth as much.

lf', thereforethe units of the scale bel fourths ofan inch, and the head of the miciometer-'Iscrew'b'e divided into fortyequal spaces, as shown in a, iig. 8, a portion of a revolution equal to one 'of them would give one one-hundredth of the unit; and the eye will readily divide these spaces into five equal parts. In a similar manner may the fractional parts of any other unit be indicatedby the graduated marks on the head oi' the micrometer-screw.

Thus, itappears, that in laying uown or measuring distances on paper, the units and tenths may be read directly on the scale, wliile the hundredths and thousandths are read on the head of the micrometer-screw. In using the first form of the micrometer the A negroove or vslotiri the headlof the indexscrew' S,

iig.. 4, is taken as a reading mark or index, and in the second forni a mark on the pen a, iig. 10, or pointholder, g. 8, serres the same purpose. In the former the micrometer-springs, 'gs. l f2, lGtssteadily.and

constantly against the micrometer-screw, so as to pro?- duce 'a smooth, steady, uniform motion. In the latter the spring. merely produces a gentle, constant pressure against the' pe'n or point-holder, 4so as .to preventall .play between them andthe screws G a'ndlM S.

. and .turning backward or forward ythe micrometerscrew M S', as occasion may require. AThe two are milled with the same numberof teeth, placed with their axes at equal `distanees from the pivot-axis. In both forms of the micrometer the pen and pointholder are -adjustable. not only is their nicetyof adjustr'nent extreme', being limited simply by a-portionof a revolution equa-l to half a tooth of the gear-screw head, but they can also be turned to'any desired degree of obIiquity; thus allowing the foot-point ofthe slide to be brought within the ftieth of an inch or less of the point ofthe pen or holder, 'and superadding to its other qualitiesthose ofthe bowpen. The second form has alsothe advantage 'over the other inhsimplieity,lightness, andcost ofcc'mstruction.4 Whenever the use of` the 'micrometer as suchis not v required, it vmay be used simplyfor adjnstment, and

distances maybe measured on .the scale directly, Ithus saving time in obtaining them, Qneof the prime excellencies of'thisinventiou eon ,ssts in the vsusceptibility which the sliding indexposesesses, by means of its friction=clamp OS andlfrictionspring S S, of any desired degree of 'frictiomsmooth and steady, with reliability and I irniness ofposition. 'lhis'isseen in abc, fig. 1; p

In position c" ilierezis Ino friction, the clamp() S Inv the second form, however,

, dividers, 'as shown and described.

'fall varieties of dividers.v But for'convenienee, certainty,and'accuracy in its The same is true of its capacity both as dividers'and as a scale for greatrvariation in length, extending from the iniuutes't'to thev greatest requisite distances. 'With a short'be'amof two incheslength, for instance,figs.

distances I know oi' nothing thatcan claim equality readilydrawn, and yet in a inomen'ts time it can be exchanged yfor one six times as long.y And, byconnectiug two togetlerby the extension-clamp, vfigs. 12 13, twofeet may be reached, if desired. Finally, if on'e ofitlie scales graduated on the beamv b'ea scale of chords, or, which isl far better, if, instead,

scales, all angles as wellas distances may be laid down upon paper or measured `with theg'reatest precision.

Hence, with theaid. of a metallic straight-edge, the instrumentfanswers all the purposes of the nieest pro tractor.

' The manner of attacninga perinanently-pivoted ad justable pen .or point-holder, Ph, to the end of beam-` JosrAH aman.

Witnesses I2' WM; S. TUCKER,- GEO. I. TUCKER.'

'Forthese causesfthere is with this instrumenta certainty in the position of the points and a neatness 1n the execution of circles andarcs unattainable in nearly 'aLTp-iication as a ,scale for measuring and laying down 6'7,'a circle of' one-fiftieth oi' au inch -radius'may be a table of chords be used in co'nnection with 'one of the. 

